Origin of Life and Cells

Question 1

What elements is living matter made from?

Answer 1

Carbon
Nitrogen
Oxygen
Hydrogen
Calcium
Phosphorus 
= 97% dry weight

Question 2

What was the Miller-Urey experiment?

Answer 2

They used a mixture of H20, CH4, NH3 and H2
They supplied it with an electric charge (lightening) and this yeilded soluble organic compounds including some amino acids

This could have taken place in hydrothermal vents - 400 degrees

Question 3

In the prebiotic era how were simple organic molecules formed?

Answer 3

From monomers in a condensation reaction to form polymers
With the rate of condensation being greater than the rate of hydrolysis

Minerals in clays would have catalysed the reactions

Question 4

What allows replication?

Answer 4

Association of complementary molecules as it can direct the assembly from smaller complementary molecules
e.g. bas pairing within DNA

Question 5

What is natural selection?

Answer 5

The survival of the fittest organisms, due to variation in genes that are favourable to a changing environment, allowing them to survive and pass on their alleles to future generations

Question 6

What did Darwin do?

Answer 6

Explored the Galapagos Islands collecting finch beaks to study
He published Origin of Species - about natural selection
And due to improved reproductive fitness, new species have arised

Evolution occurs due to variation in inherited characteristics

Question 7

What is a species?

Answer 7

A group of organisms that can interbreed with each other and are reproductively isolated

Question 8

What do cells do?

Answer 8

Carry out metabolic reactions within different compartments

Question 9

What are the advantages of compartmentation?

Answer 9

Protection from environmental forces
Maintanence of high local concentrations of components - this helps as more concentrated substances react more readily = efficient polymerisation

Question 10

What are the two types of cells?

Answer 10

Eukaryotic - a membrane enclosed nucleus holding the DNA

Prokaryotic - no nucleus

Question 11

Describe Eukaryotes?

Answer 11

Uni or Multicellular
Nucleus: condensed with proteins
More complex
10-100 μm
Diploid/Polyploid
Division: mitosis - somatic and meiosis - gametes

Question 12

Describe Prokaryotes?

Answer 12

Unicellular
DNA is free in cytoplasm as 'nucleoid'
No internal compartments
1-10 μm
Normally haploid
Simple division following DNA replication

Question 13

How can we view cells/organelles?

Answer 13

Unaided eye
Light microscope
Electron microscope

Question 14

What is the endosymbiotic theory?

Answer 14

Mitochondria and chloroplasts have been engulfed by an organism and been kept
They have their own DNA

Question 15

What is significant about energy supply?

Answer 15

ATP demand is proportional to volume
Meaning supply depends on the membrane surface area
This is lead to cells being subdivided into organelles

Question 16

Describe the mitochondria?

Answer 16

Double membrane (one invaginated)
Used for oxidative metabolism
Has an independent genome
The number of cristae per mitochondrion relates to energy demand so they can move to areas of need

Question 17

Describe the endoplasmic reticulum?

Answer 17

Smooth ER - synthesises lipids and steroids, regulates Ca2+ conc, detoxifys drugs and is used in gluconeogenesis

Rough ER - Facilitates protein synthesis/folding and transports synthesised proteins

Question 18

Describe the nucleus?

Answer 18

DNA is packed by histones into chromatin
Surrounded by a nuclear membrane containing pores to allow communication between the cytoplasm and nucleus

Heterochromatin - tightly coiled
Euchromatin - unwound and DNA can be accessed to transcribe

Question 19

Decribe the Golgi apparatus?

Answer 19

Functions in secretion and intracellular tracking of new synthesised proteins
Proteins are sorted, modified and packaged

5 functional regions of cisternae stack: cis-golgi, cid-golgi network, medial-golgi, trans-golgi and trans-golgi network
This is like a postcode (cis to trans)

Question 20

How can we categorise organisms?

Answer 20

Taxonomy - the science of biological classification

Phlogeny - relationships between organisms based on their evolutionary history

Question 21

What are the domains of life?

Answer 21

Eubacteria
Archaea
Eukarya

Question 22

What are the 4 key points of evolution?

Answer 22

Evolution is not directed towards a particular goal
Variation is among individuals
The past determines the future - preexisting elements lead to developed ones
Evolution is on going

Question 23

What biochemical tools can we use to study cells?

Answer 23

Subcellular fractionation: two types

1. Differential centrifugation
2. Isopycnic centifugation (sucrose density)

Question 24

Describe differential centrifugation?

Answer 24

1. Break open the cells in a blender/homogeniser/french press (to break the cell membrane)
2. Further homogenisation: crush and strain
3. Cetrifuge the homogenate - due to different sizes they have different sediment rates

Large cell fragments will emerge first, then heavier organelles, lighter orangelles etc.

4. Resuspend the supernautent and further isolate

Question 25

Describe isopycnic centrifugation?

Answer 25

The further purification of organelles

They are separated on a density gradient due to different buoyant densities

Question 26

How can different organelles be identified?

Answer 26

Functional assays, size and concentration of antibody binding:

Marker enzymes
SDS PAGE
Fluoresence
Antibodies
Live cell imaging

Question 27

What are marker enzymes?

Answer 27

Located exclusively in target organelles with a known activity
Therefore we can monitor enzyme activity in each fraction, this can also help indicate purity

Question 28

What is live cell imaging?

Answer 28

Using fluoresence microscopy we can track movements in real time
GFP - Green Fluorescent protein, taken from a jellyfish
GFP can be mutated to different colours